Answer is: hypotonic.
Tonicity is the relative concentration of solute (in this example sodium chloride NaCl) dissolved in solution which determine the direction of diffusion.
A hypotonic solution has a lower concentration of solutes (sodium chloride) than another solution.
Normal saline is 9 grams NaCl dissolved in one liter of water.
In this example is 4.5 grams of NaCl dissolved in one liter of water.
